MAX8631YETI(2006) 查看數據表（PDF） - Maxim Integrated

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MAX8631YETI
(Rev.:2006)

1x/1.5x/2x White LED Charge Pump with Two LDOs in 4mm x 4mm Thin QFN

Maxim Integrated 

1x/1.5x/2x White LED Charge Pump with Two

LDOs in 4mm x 4mm Thin QFN

INITIAL tHI

0

≥ 200µs

1

23

45

ENM1 AND ENM2

OR

ENF

IM_ OR IF_

tSOFT-START

32/32

31/32

30/32

tLO

500ns TO 250µs

29/32 28/32 27/32

SHUTDOWN

Figure 2. ENM_ and ENF Timing Diagram

Thermal Shutdown

The MAX8631X/Y includes a thermal-limit circuit that

shuts down the IC at approximately +160°C. Turn-on

occurs after the IC cools by approximately 20°C.

Applications Information

Setting the Main Output Current

SETM controls M1–M4 regulation current. Current flow-

ing into M1, M2, M3, and M4 is a multiple of the current

flowing out of SETM:

IM1 = IM2 = IM3 = IM4 = K x (0.6V / RSETM)

where K = 23, 69, or 230 (depending upon the state of

ENM1 and ENM2; see Table 1), and RSETM is the resis-

tor connected between SETM and GND (see the

Typical Operating Circuit).

Table 1. ENM1/ENM2 States

ENM1/ENM2 STATES BRIGHTNESS

ENM1 = low, ENM2 = low

ENM1 = low, ENM2 = high

ENM1 = high, ENM2 = low

ENM1 = high, ENM2 = high

Shutdown

1/10 brightness

3/10 brightness

Full brightness

M1–M4

CURRENT

0

23 x ISETM

69 x ISETM

230 x ISETM

Setting the Flash Output Current

SETF controls the F1–F4 regulation current. Current

flowing into F1, F2, F3, and F4 is a multiple of the cur-

rent flowing out of SETF.

IF1 = IF2 = IF3 = IF4 = N x (0.6V / RSETF)

where N = 690.

Single-Wire Pulse Dimming

For more dimming flexibility or to reduce the number of

control traces, the MAX8631X/Y supports serial pulse

dimming. Connect ENM1 and ENM2 together to enable

single-wire pulse dimming of the main LEDs (or ENF

only for single-wire pulse dimming of the flash LEDs).

When ENM1 and ENM2 (or ENF) go high simultaneous-

27 28 29 30 31 32

tHI

≥500ns

tSHDN

32/32 31/32 2ms (typ)

5/32 4/32 3/32 2/32 1/32

SHUTDOWN

ly, the main (or flash) LEDs are enabled at full bright-

ness. Each subsequent low-going pulse (500ns to

250µs pulse width) reduces the LED current by 3.125%

(1/32), so after one pulse the LED current is 96.9% (or

31/32) x ILED. The 31st pulse reduces the current to

0.03125 x ILED. The 32nd pulse sets the LED current

back to ILED. Figure 2 shows a timing diagram for sin-

gle-wire pulse dimming. Because soft-start is longer

than the initial tHI, apply dimming pulses quickly upon

startup (after initial tHI) to avoid LED current transition-

ing through full brightness.

Simple On/Off Control

If dimming control is not required, connect ENM1 to

ENM2 for simple on/off control. Drive both ENM1 and

ENM2 to a logic-level high to turn on the main LEDs.

Drive both ENM1 and ENM2 to a logic-level low to turn

off the main LEDs. ENF is the simple on/off control for

the flash LEDs. Drive ENF to a logic-level high to turn

on the flash LEDs. Drive ENF to a logic-level low to turn

off the flash LEDs. In this case, LED current is set by

the values of RSETM and RSETF.

Dimming Using PWM into ENM1

Use ENM2 for shutdown and drive ENM1 with a PWM

signal. LED brightness can be varied from 10% to full

brightness based upon the duty cycle of the PWM sig-

nal. Drive ENM2 high to keep the IC on, eliminating any

soft-start delay that would impede PWM control and

allowing a PWM frequency up to 5kHz (Figure 3).

Driving Fewer than 8 LEDs

When driving fewer than 8 LEDs, two different connec-

tion schemes can be used. The first scheme is shown

in Figure 4 where LED drivers are connected together.

This method allows increased current through the LED

and effectively allows total LED current to be ILED multi-

plied by the number of connected drivers. The second

method of connection is shown in Figure 5 where stan-

dard white LEDs are used and fewer than 8 are con-

nected. This scheme does not alter current through

each LED but ensures that the unused LED driver is

properly disabled.

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